Implement Enable property values "inactive" and "off" for uicontrol Edit (bug #57128) * BaseControl.cc (updatePalette): Call setColor() with additional argument of "QPalette::Active" and again with "QPalette::Inactive" so that colors are set only for specific roles. When Qt widget disabled it should now go gray. * BaseControl.cc (init): Call 'setEnabled (! properties.enable_is ("off"))' so that "Inactive" value still causes Qt Widget to be enabled. * BaseControl.cc (update): Call 'setEnabled (! properties.enable_is ("off"))' so that "Inactive" value still causes Qt Widget to be enabled. * EditControl.cc (init): Check Octave "Enable" property and call Qt setReadOnly() if value is "Inactive", but otherwise call Qt setEnabled() with property value. * EditControl.cc (updateSingleLine, updateMultiLine): Check Octave "Enable" property and call Qt setReadOnly() if value is "Inactive", but otherwise call Qt setEnabled() with property value.

%!function rval = sggval (val)
%!  global gval
%!  if (nargin == 1)
%!    gval = val;
%!  else
%!    rval = gval;
%!  endif
%!endfunction

%!test
%! global gval
%! assert (isempty (gval))
%! sggval (13);
%! assert (sggval (), 13);
%! assert (gval, 13);
%! clear global gval
%! assert (sggval (), [])
%! gval = 42;
%! assert (sggval (), []);
%! clear gval
%! global gval
%! gval = 42;
%! assert (sggval (), 42);
%! clear -global gval;  # cleanup after test